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Mobile elements and chromosomal changes associated with MLS resistance phenotypes of invasive pneumococci recovered

Paulina A Hawkins1, Sopio Chochua, Delois Jackson

  • 11 Hubert Department of Global Health, Rollins School of Public Health, Emory University , Atlanta, Georgia .

Microbial Drug Resistance (Larchmont, N.Y.)
|August 14, 2014
PubMed

Insights

Pneumococcal resistance to macrolide antibiotics is primarily due to mef genes or erm methylases. This study identified novel ribosomal mutations in Streptococcus pneumoniae, expanding our understanding of antibiotic resistance mechanisms.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Antimicrobial Resistance

Background:

  • Pneumococcal macrolide resistance presents as M phenotype (mef gene) or MLSB phenotype (erm methylase).
  • Antibiotic resistance can also arise from ribosomal target mutations (23S rRNA, L4, L22 riboproteins).
  • Understanding resistance mechanisms is crucial for effective treatment of invasive pneumococcal disease.

Purpose of the Study:

  • To investigate the mechanisms of macrolide and quinupristin-dalfopristin resistance in invasive Streptococcus pneumoniae isolates.
  • To identify novel genetic determinants contributing to antibiotic resistance in pneumococci.

Main Methods:

  • Screening of 4,535 erythromycin-resistant and 18 quinupristin-dalfopristin-nonsusceptible invasive pneumococcal isolates.
  • Polymerase chain reaction (PCR) to detect known resistance genes (mef, ermB, ermA, ermT, cfr, lsaC, vgaA).
  • Analysis of chromosomal mutations in 23S rRNA, rplD, and rplV genes.

Main Results:

  • Prevalence of resistance genes: mef (66.2%), ermB (17.8%), both mef and ermB (15.1%) in erythromycin-resistant isolates.
  • Chromosomal mutations were identified in 25 erythromycin-resistant isolates and 14 quinupristin-dalfopristin-nonsusceptible isolates.
  • A total of 28 mutations were found, with 13 previously undescribed in Streptococcus pneumoniae.

Conclusions:

  • The study highlights the diverse genetic basis of macrolide and quinupristin-dalfopristin resistance in pneumococci.
  • Novel chromosomal mutations contribute significantly to antibiotic resistance, requiring further investigation.
  • Transformation assays are needed to confirm the role of newly identified mutations in resistance.

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